The present invention relates to a divider circuit arrangement and particularly, but not exclusively, to a dual branch receiver having such a divider circuit arrangement.
In analogue signal processing, a division function is often used for normalising signal amplitudes. One disadvantage associated with the division function is the possibility that the resulting quotient will go to infinity if the divisor becomes zero. When this occurs, the circuit that performs this normalisation function will swing to its extreme state, for example, saturation of an analogue circuit. In practice, special precautions are usually taken to avoid this possible overflow state.
European Patent Specification No. 0075707B1 discloses a ring interferometer in which non-zero divide by zero is avoided. Light from a laser is arranged to pass through two spatially separated, partially transmitting mirrors. Two opto-electronic sensors detect light reflected by these mirrors. The outputs from these sensors are coupled to quotient forming means. In order to avoid a "divide by zero" problem an output of one of the sensors forms the dividend and the divisor is formed by the sum of proportionate parts of the signals appearing at the outputs of the sensors.
In the field of telecommunications, for example in a dual branch receiver or demodulator of a type disclosed by J. K. Goatcher, M. W. Neale and I.A.W. Vance in an article entitled "Noise considerations in an integrated circuit VHF radio receiver" in the Proceedings of the IERE Clerk Maxwell Commemorative Conference on Radio Receivers and Associated Systems (IERE Proceedings 50), University of Leeds, 7th to 9th July 1981, pages 49 to 51 a signal is normalised by it being divided using a divisor formed by the sum of the squares of the in-band components of the quadrature related signals which have been produced by mixing an input signal down to baseband. If the input signal is lost due to say a fade which may occur in a mobile environment then a divide by zero situation occurs. If such a situation should occur frequently then an inpleasant audio output may occur.